1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image on a sheet using an intermediate transfer belt.
2. Description of the Related Art
Among image forming apparatuses that form an image on a sheet using an intermediate transfer belt, apparatuses that adopt a method of separating a sheet that has been stuck to the belt surface of the intermediate transfer belt at the feeding time from the belt surface by pressing a nail-like member or the like against the belt surface using, for example, a solenoid have been available. In some cases, the sheet may be stuck fast to the belt surface in such a manner that any portions of the sheet are not apart from the belt surface. The thicknesses of most of the sheet that are easily stuck to the belt surface as described above are as thin as about 0.1 mm or less. Therefore, the nail-like member may scratch the belt surface at the time when the thin sheet is separated from the belt surface. The scratch on the belt surface prevents good toner adhesion, resulting in image deterioration. On the other hand, when a configuration that the nail-like member is disposed near the belt surface in a fixed manner without using the solenoid is adopted, it is necessary to strictly adjust the disposition of the nail-like member in the manufacturing process. In order to cope with the problem, a configuration in which a sensor that detects that a sheet has been stuck to the belt surface is provided and the entire function of the apparatus is halted when the sensor detects the sheet stuck to the belt surface is disclosed (for example, see Japanese Patent Laid-Open Publication No. 11-59962 (pages 4 to 8, FIG. 1)).
However, the intermediate transfer belt is in contact with a photoreceptor drum or the like, so that it is impossible to stop the intermediate transfer belt instantaneously due to influence of inertial force or the like caused by own weight of the photoreceptor drum even if the entire system is halted at the time when the adhesion of the sheet to the belt surface is detected. In this case, it is impossible to give enough braking force to the sheet, with the result that the sheet may not be stopped at a desired position and may enter the inside of the apparatus while being stuck fast to the belt surface.
In the case where the sheet has entered the inside of the apparatus with the movement of the belt surface as described above, the apparatus may break down. Therefore, it is necessary to prevent the sheet from entering the inside of the apparatus as much as possible.